(1E)-1-[(3'aS,4'R,5'R,6'aR)-5'-[[(1,1-Dimethylethyl)dimethylsilyl]oxy]hexahydro-5,5-dimethylspiro[1,3-dioxane-2,2'(1'H)-pentalen]-4'-yl]-4-methyl-1-octen-6-yn-3-one